Recent developments in the study of the structure and function of muscle sarcoplasmic reticulum have led to the resolution of molecular components involved in Ca2 ion transport. Very little is known, however about the mechanism by which Ca2 ion is released from the sarcoplasmic reticulum, which presumably is a key process in muscle contraction. In order to gain further understanding of the molecular mechanism of Ca2 ion transport and release in the sarcoplasmic reticulum, we plan to study: 1) the molecular structure and disposition of some membrane components of the protein, viz. the ATPase enzyme, calsequestrin and glycoprotein; 2) the interaction of these components with phospholipids in an effort to reconstitute vesicles capable of Ca2 ion transport and release under physiological conditions; 3) intermediate steps in the ATPase and CA2 ion transport process and their relation to conformational changes in the enzyme; and 4) the roles membrane components play in the Ca2 ion release mechanism.